1. Field of the Invention
This invention relates to a fuel invasion preventer for a solenoid fuel injection valve and, more particularly, to a fuel invasion preventer for preventing fuel from invading the solenoid actuator of a solenoid fuel injection valve.
2. Prior Art
A general explanation of the prior art low-pressure solenoid fuel injection valve as exemplified by a low pressure nozzle for gasoline engines will be given with respect to FIG. 6.
FIG. 6 is a vertical sectional view of a solenoid fuel injection valve 1 having a valve housing 2, a connector 3, a fuel supply pipe 4 made of a magnetic material, a valve stop 5, a valve seat 6 and a nozzle cover 7.
A solenoid actuator 8 is provided between the valve housing 2 and the fuel supply pipe 4 made of magnetic material.
The solenoid actuator 8 consists of a bobbin 9 (made of a nonmagnetic material such as polyamide resin and has the fuel supply pipe 4 passing through its interior) and a solenoid winding 10 wound on the bobbin 9. The solenoid actuator 8 is energized and de-energized by a control signal input through the connector 3.
An armature 11 is positioned immediately below the fuel supply pipe 4 (as seen in FIG. 6) and a needle valve 12 integrally movable with the armature 11 is biased toward a nozzle 14 at the tip of a valve seat 6 by a valve spring 13 so as to be seated on the valve seat 6.
Fuel is supplied from the top of the fuel supply pipe 4 to a first fuel passage 15, from the first fuel passage 15 to a second fuel passage 16 inside the armature 11 and then to a third fuel passage 17 between the valve seat 6 and the needle valve 12. When the solenoid actuator 8 is excited, the armature 11 and needle valve 12 are lifted (by the amount of lift L) and fuel is injected into an air intake manifold (not shown) from the nozzle 14.
If fuel should invade the solenoid actuator 8, particularly the solenoid winding 10 thereof, the solenoid winding 10 is liable to be corroded and made inoperative by fuel additives that are amine based of have a sulfate radical.
In addition, leakage of fuel through the solenoid actuator 8 to the connector 3 must be avoided for ensuring proper performance of the solenoid fuel injection valve 1.
Invasion of fuel from a continuous space 20 communicating with the first fuel passages 15, 16 and 17 into the solenoid actuator 8, particularly the solenoid winding 10, is therefore prevented by providing a first O-ring 18 between the bobbin 9 and the outer wail of the fuel supply pipe 4 and providing a second O-ring 19 between the bobbin 9 and the inner wall of the valve housing 2.
When necessary the invasion of fuel is further contained by providing a molded gasket 21 for protecting the outer periphery of the solenoid actuator 8, as described, for example, in Japanese Utility Model Public Disclosures Hei 4-107476 and Hei 5-42667.
Generally, no pronounced fuel invasion problem arises in the solenoid fuel injection valve 1 assembled in the foregoing manner when a low injection pressure is present. However, in high-pressure solenoid fuel injection valve applications, such as for injecting fuel directly into the cylinder of a gasoline engine, the injection pressure will be higher than that which conventional, commercially available solenoid fuel injection valves can handle. Accordingly, it would not be possible to prevent fuel invasion and leakage merely by utilizing the first O-ring 18 and the second O-ring 19, with or without the molded gasket 21, so described above.
Even in a low injection pressure solenoid fuel injection valve application, there is some possibility of damage to the actuator 8 of the prior art valve from additives owing to fuel invasion or leakage. It is therefore prudent to implement measures for preventing degradation of the solenoid actuator 8 irrespective of the fuel pressure.
This invention was developed to address the foregoing problems. One object of the present invention is to provide a fuel invasion preventer for a solenoid fuel injection valve which can prevent invasion and leakage of fuel into the solenoid actuator with a simple structural arrangement.
Another object of the present invention is to provide a fuel invasion preventer for a solenoid fuel injection valve which can reliably prevent fuel invasion and leakage at increased fuel pressures.
Another object of the present invention is to provide a low-cost fuel invasion preventer for a solenoid fuel injection valve.